多晶石墨烯能带结构的外应变和失配应变调谐
Tunable Band Structures of Polycrystalline Graphene by External and Mismatch Strains
摘要：
缺乏带隙在很大程度上限制了石墨烯在电子器件中的应用。先前的研究表明，多晶石墨烯中的晶界（GBs）可以显著改变石墨烯的电学性质。在这里，我们调查的能带结构的多晶石墨烯调谐外部施加的应变和内在的失配应变在GB的密度泛函理论（DFT）计算。我们发现，即使在单轴和双轴应变很大的情况下，具有对称GB的石墨烯通常也具有零带隙。然而，一些特定的不对称GB可以打开石墨烯中的带隙，并且它们的能带结构可以通过外部应变基本上调谐。在匹配扶手椅结构GB（5，5）中观察到最大带隙为0.19 eV|（3，7），当单轴应变增加到9%时，取向差θ= 13 o。虽然失配应变在非对称晶界中是不可避免的，但它对多晶石墨烯的带隙的影响很小。
英文摘要：
Lacking a band gap largely limits the application of graphene in electronic devices. Previous study shows that grain boundaries (GBs) in polycrystalline graphene can dramatically alter the electrical properties of graphene. Here, we investigate the band structure of polycrystalline graphene tuned by externally imposed strains and intrinsic mismatch strains at the GB by density functional theory (DFT) calculations. We found that graphene with symmetrical GBs typically has zero band gap even with large uniaxial and biaxial strain. However, some particular asymmetrical GBs can open a band gap in graphene and their band structures can be substantially tuned by external strains. A maximum band gap about 0.19 eV was observed in matched-armchair GB (5, 5) | (3, 7) with a misorientation of θ=13o when the applied uniaxial strain increases to 9%. Although mismatch strain is inevitable in asymmetrical GBs, it has a small influence on the band gap of polycrystalline graphene.
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